Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2009
Publication Date: 7/1/2009
Citation: Ngwa, A.T., Dawson, L.J., Puchala, R., Detweiler, G., Merkel, R.C., Wang, Z., Tesfai, K., Sahlu, T., Ferrell, C.L., Goetsch, A.L. 2009. Effects of Stage of Lactation and Dietary Forage Level on Body Composition of Alpine Dairy Goats. Journal of Dairy Science. 92(7):3374-3385. Interpretive Summary: A complete understanding of the composition of tissue being accreted or mobilized is necessary to determine dietary energy needs. Factors that may influence the composition of tissue being lost or gained by lactating dairy goats include diet quality and stage of lactation. Results of this study indicate that considerable internal fat is mobilized in early lactation particularly with diets moderate to high in forage, with more rapid and a greater magnitude of repletion by does consuming diets lower in forage. The concentration of energy in tissue mobilized or accreted was much greater in late than early and mid-lactation.
Technical Abstract: Multiparous Alpine does (42) were used to determine how stage of lactation and dietary forage level affect body composition. Initial measures were made with six does a few days after kidding (0 mo). Before parturition does were fed a 50% concentrate diet free-choice. Eighteen does were fed a 40% forage diet (40F) and 18 received a diet with 60% forage (60F) for approximately 2, 4, or 6 mo of lactation. The 60F diet had 20% more dehydrated alfalfa pellets than the 40F diet, with higher levels of corn and soybean meal and inclusion of supplemental fat in the 40F diet. Intake of dry matter was greater for 60F vs. 40F, average daily gain tended to be affected by an interaction between diet and month (0, 24, 121, -61, 46, and 73 g), and 4% fat-corrected milk was less in mo 5-6 than earlier. Internal fat mass was greatest among times at 6 mo and greater for 40F vs. 60F. Mass of the gastrointestinal tract was less for 40F than for 60F and decreased with increasing time in lactation. Concentrations of fat in the carcass (13.8, 13.1, 16.5, 11.2, 11.5, and 14.4%), noncarcass tissues (18.6, 24.2, 33.3, 14.3, 16.5, and 24.5%), and empty body (16.5, 18.7, 25.2, 12.9, 14.1, and 19.5% for 40F:2 mo, 40F:4 mo, 40F:6 mo, 60F:2 mo, 60F:4 mo, and 60F:6 mo, respectively) were affected by stage of lactation and diet. Based on daily change in tissue mass and energy, energy concentration in tissue mobilized or accreted was 16, 20, and 32 MJ/kg in 1-2, 3-4, and 5-6 mo of lactation, respectively. In conclusion, based on tissue mass more energy was expended by the GIT with 60F vs. 40F. Considerable internal fat is mobilized in early lactation particularly with diets moderate to high in forage, with more rapid and a greater magnitude of repletion by does consuming diets lower in forage. The concentration of energy in tissue mobilized or accreted may vary with stage of lactation.